Hydroxyapatite [Ca10(PO4)6(OH)2], obtainable by sintering a calcium phosphate composition, has a composition nearly the same as inorganic components such as bones or teeth, and has a bioactivity that is capable of being directly combined with tooth tissues so that the hydroxyapatite has been utilized as restorative materials for bone-defect parts or bone-gap parts. However, while a material made of the hydroxyapatite as mentioned above has excellent biocompatibility, the material may have difficulty in moldability in some cases in order to apply the material to a site having a complicated shape.
On the other hand, among the calcium phosphate compositions, it is known that a calcium phosphate composition of cement type, in other words, the composition having curability, gradually converts to hydroxyapatite in a live body or oral cavity, thereby making it possible to integrate with the biological hard tissues while keeping its form. The calcium phosphate composition as described above has not only excellent biocompatibility but also moldability, so that the application of the composition to a site having complicated shape is facilitated.
For example, Patent Publication 1 describes that a mixture of tetracalcium phosphate and dicalcium phosphate anhydrous is rapidly auto-cured in the presence of water, thereby forming hydroxyapatite having excellent mechanical strength.